1. Field of the Invention
The present invention relates to a copier, printer, facsimile apparatus or similar image forming apparatus, a process cartridge and a cleaningless system.
2. Description of the Background Art
One type of conventional image forming apparatuses is configured to form an electric field for image transfer between a photoconductive element and an image transfer medium moving in contact with the photoconductive element to thereby transfer a toner image from the photoconductive element to the image transfer medium. In such an electrostatic image transfer type of image forming apparatus, residual toner is often left on the surface of the photoconductive element after the transfer of the toner image. Should the surface portion of the photoconductive element where the residual toner exists be subject to the next image forming cycle, irregular charging or similar defective charging would occur at the above surface portion, degrading image quality. To solve this problem, it has been customary to remove the residual toner with a cleaning device located at a position where it faces the photoconductive element between an image transferring zone and a charging zone.
However, the problem with the cleaning device described above is that it needs spaces for accommodating a waste toner tank for storing the residual toner collected from the photoconductive element, a conduit for reusing the collected toner and so forth, increasing the overall size of the image forming apparatus. This is particularly true with a tandem image forming apparatus in which the cleaning device must be assigned to each of a plurality of photoconductive elements.
In light of the above, Japanese Patent No. 3091323, for example, discloses an image forming apparatus of the type causing a developing device to collect residual toner from the surface of a photoconductive element. This type of toner collecting system causes the developing device to play the role of cleaning device at the same time and therefore does not need a cleaning device independent of the developing device. Further, spaces for accommodating the conduit for the conveyance of the collected residual toner and so forth are not necessary. Therefore, this type of toner collecting system contributes a great deal to the size reduction of an image forming apparatus.
Recently, however, the diameter of a developing roller and that of a photoconductive element are decreasing in parallel with the size reduction of an image forming apparatus. This brings about a problem that a developing zone where the photoconductive element and developing roller are closest to each other is narrowed and lowers the collection ratio of the residual toner from the photoconductive element. Consequently, the residual toner not collected accumulates on the photoconductive element, resulting in background contamination and other image defects and toner scattering and other mechanical troubles.